The present invention relates generally to hand power tools for flat machining.
One of such hand power tools is disclosed, for example in the British Patent Document GB-A-686 363. U.S. Pat. No. 3,160,995 discloses a hand power tool for grinding surfaces close to edges, in particular in corners or along hollow grooves. The hand power tool has a grinding plate with a triangular base surface. The working movement is performed about a stationary axis which is arranged perpendicular to the base surface in a reciprocating swinging manner. The axis of the grinding plate extends geometrically near and through a forwardly facing corner. The angle of the corner in the front region of the grinding plate is smaller than 90.degree., and therefore the grinding plate is usable up to the outermost edge-closed region of corners or hollow grooves for grinding. In a further development of a hand powered tools with the grinding plate having a geometrically centrally extending axis, the edge of the grinding tool is curved as in a bracket iron, for edge-flush grinding at locations which are difficult to access. The base contour of the grinding plate formed as an isosceles triangle with curved side edges has, as all such triangles, three corner angles each smaller than 90.degree..
Moreover hand power tools with rectangular grinding plates are also known. They have an eccentric drive and perform a gyrating, circulating movement. These hand power tools are known as vibrating grinders, while thereto does not perform on vibrating movement in its accurate sense.
In a further development of the vibrating grinders, eccentric grinders have been developed with non-gyrating, circulating and rotating grinding plate. Its movement is controllable by adjustment of several different working steps.
U.S. Pat. No. 4,782,632 discloses a grinding power tool machine with a rotatable grinding plate which is driven through a bendable shaft. It is covered by a shell-shape stationary protective hood which is supported with its shell-shaped edge on a workpiece to be machined and connected with a dust aspirating device by tubular pipes and a hose for aspiration of the produced grinding dust.
The known hand power tools are efficient, but they are relatively expensive. They require an auxiliary tool for a tool exchange, for example for exchange of the grinding plates. Since such an auxiliary tool, for example a screwdriver, is not a always available and is easy to be lost, the exchange of the grinding plates is complicated and time consuming.